An economical and effective refastenable adhesive tape closure system has been desired for use in disposable garment articles such as disposable diapers. In diapers, the adhesive tape is employed to fasten the diaper around the waist of an infant. This tape is formulated to be sufficiently tacky to hold the tape securely in place while in storage, and to insure against disengagement or displacement once the diaper is put on the infant. The backing sheet against which the adhesive is fastened are made of a flexible, liquid impermeable film, such as polyethylene. This film is very thin to reduce costs and to provide other characteristics such as flexibility and low rattle. Typically the film is about 0.001 inches (0.00254 cm) thick.
If one desires to inspect or adjust the diaper after the tape has been fastened, the process of peeling the tape from the film backing ordinarily stretches and tears the film because the film has a low tensile load-bearing capability. Further use of the diaper is then impractical; the film is either torn and weakened, or the adhesive areas of the tape are covered by pieces of torn film. Since the film or the tape has been damaged by the removal process, the diaper must be replaced with a new one even though the other diaper components remain substantially undamaged or unsoiled and are otherwise functional.
One suggested solution to the problem has been to use tape with a pressure-sensitive adhesive with moderate tack and peel strength. Such tape would permit peeling the tape off without damage to the film or tape and would thereby provide refastenability. This technique, however, has not been completely satisfactory because the tapes tend to prematurely release during use.
Another suggested technique has been to treat the tape-receiving surface of the film backing sheet with a release coating or, alternatively, interposing in the tape-receiving area another tape component having a release treated surface. Such a technique is disclosed, for example, in U.S. Pat. No. 4,020,842 to Richman, et al.; U.S. Pat. No. 4,043,340 to Cepuratis; and U.S. Pat. No. 4,049,001 to Tritsch. This technique, however, can allow inadvertent and premature release.
A further technique has been to reinforce the adhesive tape attachment zone with a reinforcing layer. For example, U.S. Pat. No. 3,867,940 to Mesek, et al. suggests adhesively laminating a flexible structural material to the film. U.S. Pat. No. 4,296,750 issued Oct. 27, 1981 to Woon, et al. discloses the use of a hot melt adhesive layer to reinforce a plastic film.
Instead of reinforcing the film backing, the strength of the film itself may be increased by increasing the film thickness. This technique, however, is expensive and uneconomical.
The following documents discuss the curing of urethane acrylate oligomers with electron beam radiation: W. Oraby and W. K. Walsh, "Elastomeric Electron Beam-Cured Coatings: Structure-Property Relationships. I. Oligomer Structure", Journal of Applied Polymer Science, Vol. 23, pages 3227-3242 (1979). W. Oraby and W. K. Walsh, "Elastomeric Electron Beam-Cured Coatings: Structure-Property Relationships. II. Chain Transfer Agents", Journal of Applied Polymer Science, Vol. 23, pages 3243-3254 (1979).
James V. Crivello, "Recent Progress in UV Curing", American Chemical Society Division Organic Coating Preparation, Vol. 41, page 560 (1979) discusses the UV-curing of surface coating. Curable resins discussed in this paper include acylates, vinyl esters and N-vinyl pyrrolidone.
U.S. Pat. No. 4,291,087 issued Sept. 22, 1981 to C. E. Warburton, Jr. discloses nonwoven fabrics which are impregnated with a water insoluble binder composed of a polymer curable by electron beam or ultraviolent radiation.
Conventional techniques, such as those taught by the above references, have not provided a sufficiently economical and effective adhesive tape closure system which is readily releasable while providing a closure bond strong enough to avoid undesired, premature release. In addition, these conventional techniques have not been able to effectively reinforce a thin, flexible film substrate without causing unsightly distortions of the substrate material or excessive stiffening of the material.